When the Lulla doll hit the market in 2016, it sold out within two weeks of its release, prompting eBay bidding wars that drove up the price of the $69 doll to $665. These bidders were likely exhausted new parents, who would do anything to get a few more hours of shut-eye.

That’s because the Lulla is scientifically proven to help preemies, newborns, babies, and toddlers sleep better. The doll, which took three years of extensive user testing to develop, comes with a built-in noisemaker that provides eight hours of recorded sounds of breathing and heartbeat. This mimics the sounds that a fetus hears inside its mother’s uterus, and will stabilize the baby’s own breathing and heartbeat.

RoRo, the Icelandic company that created the doll, spent a lot of time thinking about the physical characteristics of the doll. Its face is both ethnically ambiguous and gender neutral (it has blue hair!), but it still manages to look cute and attractive to babies. The company also said that, in its user studies, 73% of parents reported that their child slept longer with the doll. The dolls have been particularly helpful to premature babies, and RoRo has donated them to hospitals in Iceland, orphanages in Africa, and needy families in Australia.

After that initial run of products sold out, RoRo has been trying to keep up with demand and has grown 2,400%. The doll has recently come back in stock in time for the holidays, which hopefully means that some new parents will be getting the gift of sleep this Christmas.ES